The present invention relates to a liquid cooling system, and, in particular, to a liquid cooling system that is suitable for use in an ultra-small and/or thin electronic device.
Semiconductor devices, that are used in electronic devices, such as a computer, etc., generate heat during their operation. In particular, high-integrated semiconductor devices, in recent years, have produced an increased amount of heat generation. Since the semiconductor devices will be damaged and incapable of functioning if the temperature thereof exceeds a certain value, cooling is necessary to prevent damage to semiconductor devices having a large amount of heat generation during use.
For cooling the semiconductor devices of an electronic apparatus, there are various known techniques, such as thermal conduction or air-cooling, or the use of a heat pipe, or liquid cooling.
Cooling by thermal conduction is achieved by using materials having a large thermal conductivity along the heat radiating route, extending from the semiconductor device to the outside of the electronic apparatus. This method has been suitable for a so-called compact electronic apparatus, in which eat generation is relatively small, such as a notebook-type personal computer.
With cooling by the use of forced air, an air blower or fan is provided inside the electronic apparatus, thereby achieving a cooling of the semiconductor device therein by forced circulation of air thereon. This method is adopted widely for the cooling of semiconductor devices having a higher amount of heat generation, and it also has been applied to a personal computer by making the air blower small and thin in size.
Cooling with the use of a heat pipe involves carrying heat out to the outside of the electronic apparatus by means of coolant enclosed within a pipe, as described in Japanese Patent Laying-Open No. Hei 1-184699 (1989), and Japanese Patent Laying-Open No. Hei 2-244748 (1989), for example. With this method, since there is no part capable of consuming electric power therein, such as an air blower or fan, such a cooling device has good efficiency, i.e., it increases the cooling through thermal conduction. However, with this method, there is a limit to the amount of heat that can be transferred.
Cooling by means of a liquid coolant is suitable for the cooling of a semiconductor device which generates a large amount of heat, and such a cooling device is described, for example, in Japanese Patent Laying-Open No. Hei 5-1335454 (1993), Japanese Patent Laying-Open No. Hei 6-97338 (1994), Japanese Patent Laying-Open No. Hei 6-125188 (1994), and Japanese Patent Laying-Open No. Hei 10-2 13370 (1998). However, such a cooling system using a liquid coolant has been restricted as to its field of utilization, such as to a large-scale computer. This is because the cooling system using a liquid coolant requires a large number of parts, such as a pump, a pipe system, heat radiation fins, etc., which are used exclusively for cooling, and so the apparatus comes to be large in size. Thus, it is difficult to maintain a satisfactory reliability when using liquid for cooling compared to other methods. It is also one reason why, on the commercial market, no semiconductor device requiring such a high level of cooling employs a liquid coolant system, other than in the field of the large-scale computers.
A technique for adapting the liquid cooling to a small-sized apparatus, including a notebook-sized personal computer, is described in Japanese Patent Laying-Open No. Hei 6-266474 (1994). In this cooling device, a header attached onto the semiconductor device and a heat radiation pipe separately located from it are connected with each other by means of a flexible tube to form a cooling system, and cooling is obtained by causing liquid coolant to flow therethrough.
However, there has been a remarkable increase in the heat generation produced from semiconductor devices which are used in electronic devices, such as a personal computer, a server computer, a work station, etc., in recent years. In addition, there has been a demand for electronic devices, such as a notebook-type personal computer, to be ultra-small and thin in size as well. For cooling the semiconductor devices used in those devices, various cooling methods have been adopted, such as thermal conduction, air-cooling, and/or the use of a heat pipe, as mentioned previously, however, the capacity of such cooling is still insufficient.
Also, for applying a liquid cooling system, which has been conventionally used in a large-scaled computer, to those electronic devices that are ultra-small and thin in size, it is a necessary condition that the liquid cooling system itself be ultra-small and thin in size. With such a system, the amount of liquid coolant retained therein is remarkably small, such as about {fraction (1/10,000)}. Because of the small amount of liquid coolant, the quality of the liquid coolant is easily lowered or degraded, even with a very small amount of elusion of corrosive ions from material that is in contact with the liquid coolant, which promotes corrosion in the heat receiving jacket and/or the heat radiation pipe, both of which are typically made of metal. Since leakage of the liquid coolant undesirably affects the function of the apparatus, this leakage must be suppressed, however, measures taken to avoid this problem have been insufficient, according to conventional techniques.
Accordingly, an object of the present invention is to provide a liquid cooling system which is suitable for cooling a semiconductor device or the like, of the type which is used in electronic devices that are ultra-small and thin in size, and which is also capable of suppressing any influence on the electronic device due to corrosion, thereby ensuring the dependability of the system as a whole, and further to provide a personal computer equipped therewith.
For solving such problems, as mentioned above, according to the present invention, the tendency for corrosion to occur can be controlled, thereby providing a system which is effectively protected from corrosion, even for a computer having a structure which is small and thin in size.
In more detail, the present invention provides a liquid cooling system having a pump for supplying cooling liquid; a heat receiving jacket being supplied with said cooling liquid and position to receive heat generated from a heat generation body; a heat radiation pipe for radiating heat which is supplied thereto by cooling liquid passing through said heat receiving jacket; and a passage for circulating the cooling liquid passing through said heat radiation pipe into said pump, wherein said heat radiation pipe is made of a material having a corrosion resistance that is higher than that of said heat receiving jacket. Further, it is possible to construct the heat receiving jacket so as to be surrounded by a waterproof sheet, thereby to improve the reliability thereof.
With the corrosion resistance mentioned above, consideration must be given to pitting corrosion with respect to ions dissolved in the cooling liquid (in particular, halogen group ions, such as fluorine, chlorine, etc., of organic matter, including rubber and plastics, dissolving from an area that is in contact with the liquid). As an example, the heat receiving jacket may be made of material, mainly containing aluminum as a constituent component thereof, while said heat radiation pipe is made of a stainless material. However, on the other hand, by taking the importance of the thermal conductivity thereof into consideration, although it lowers the characteristic of corrosion resistance from that mentioned above, it may be possible, for example, to make the heat receiving jacket of a material, mainly containing copper as a constituent component thereof, while the heat radiation pipe is made of a stainless material. As another example, though there may be a possibility of lowering the characteristic of corrosion resistance, it is also possible for the heat receiving jacket to be made of a material, mainly containing aluminum as a constituent component thereof, while the heat radiation pipe is made of a material, mainly containing copper as a constituent component thereof, from the same viewpoint as indicated above. However, in this case, it is preferable to take a countermeasure, such as, adding an anticorrosive agent and/or a corrosion inhibiter agent to the copper, from the viewpoint of the corrosion resistance thereof.
According to the present invention, the heat radiation pipe is made of a material having a corrosion resistance that is higher than that of the heat receiving jacket; and the thickness from the cooling liquid passage up to the surface of said jacket in the heat receiving jacket is greater than the thickness from the cooling liquid passage up to the surface of the heat radiation pipe in the heat radiation pipe.
Alternatively, it is also possible for the heat receiving jacket to be made of a material, mainly containing copper as a constituent component thereof, while the heat radiation pipe is also made of a material, mainly containing copper as a constituent component thereof. However, in this case, it is preferable to introduce a corrosion inhibiter agent into the material of the copper group, in addition thereto, from the viewpoint of increasing the inhibiting corrosion effect.
Alternatively, it is also possible for the heat receiving jacket to be made of a material, mainly containing aluminum as a constituent component thereof, while the heat radiation pipe is also made of a material, mainly containing aluminum as a constituent component thereof. However, in this case, it is preferable to introduce a corrosion inhibiter agent into the material of the aluminum group, in addition thereto, from the viewpoint of increasing the inhibiting corrosion effect.
And, more preferably, the present invention provides a personal computer including a semiconductor element, a signal input portion and a display device; and, further including a heat receiving jacket supplied with cooling liquid and position to receive heat generated from a heat generation body; a heat radiation pipe for radiating heat which is supplied by the cooling liquid passing through said heat receiving jacket; and a passage for circulating the cooling liquid passing through said heat radiation pipe into said pump, in addition to those features mentioned above.
As an example of a notebook-type personal computer, there is provided a personal computer having a main body including a semiconductor element and a signal input portion; a display device, having a display portion, connected with said main body through a movable mechanism; a pump for emitting cooling liquid; a heat receiving jacket disposed within said main body and supplied with said cooling liquid, said heat receiving jacket being positioned to receive heat generated within said semiconductor element;,a heat radiation pipe disposed on a back surface of said display portion of said display device for radiating heat which is supplied by the cooling liquid passing through said heat receiving jacket; and a passage for circulating the cooling liquid passing through said heat radiation pipe into said pump. In more detail, the heat receiving jacket is made of a material, mainly containing copper as a constituent component thereof, while said heat radiation pipe is also made of a material, mainly containing copper as a constituent component thereof; and, the thickness from said cooling liquid passage up to the surface of said jacket in said heat receiving jacket is greater than the thickness from said cooling liquid passage up to the surface of said heat radiation pipe in said heat radiation pipe.